Melting apparatus and method for melting metal

ABSTRACT

Melting apparatus for melting a metal, such as aluminium, comprising a melting chamber, a burner chamber and a passage which extends between the melting chamber and the burner chamber and which has an inlet opening on the melting-chamber side and an outlet opening on the burner chamber side for allowing molten metal to pass from the melting chamber to the burner chamber, circulation means being suitable for transferring molten metal from a first or suction connection to the burner chamber to a second or pressure connection to the melting chamber. According to the invention, the residual bath when changing the metal composition ins minimized and productivity maximized.

The invention relates to a melting apparatus for melting a metal, suchas aluminium, comprising a melting chamber, a burner chamber and apassage which extends between the melting chamber and the burner chamberand which has an inlet opening on the melting-chamber side and an outletopening on the burner-chamber side for allowing molten metal to passfrom the melting chamber to the burner chamber, and further comprisingcirculation means which are suitable for transferring molten metal to asecond or pressure connection of the melting chamber from a first orsuction connection of the burner chamber. Also the invention relates toa method for melting metal.

Such a melting apparatus is disclosed in U.S. Pat. No. 4,491,474.

Metal scrap to be melted is introduced into the melting chamber via aclosable charging opening in a wall of the melting chamber.

In this operation, the metal scrap may first be placed on a loadingincline adjoining the base of the furnace vessel in order to preheat it,after which it is pushed into the bath by metal scrap introduced later.The metal scrap can also be introduced directly into the bath.

As a consequence of the high temperatures in the melting chamber, someof the organic and combustible materials entrained with the metal scrapor adhering to it pyrolyses or, if oxygen is present, burns. Otherimpurities and oxides finish up in a slag layer on the molten metal, butcannot reach the burner chamber as a result of the presence of thepartition.

In the burner chamber, burners are fitted to heat the molten metal. Themelting capacity of the melting apparatus increases with increasingsurface area of the bath in view of the transfer of heat generated bythe burners to the metal. Burner offgases can be removed directly to theoutside. It is also possible to pass the offgases through the meltingchamber in order to preheat the metal scrap.

As the result of convection, molten metal flows within the meltingchamber and within the burner chamber and between these two chambers.Molten metal which flows from the burner chamber to the melting chambergives off heat there to the part of the bath in the melting chamber andto metal scrap still to be melted and flows back to the burner chamber.

The metal to be melted, such as aluminium, for use in such a furnaceapparatus is generally metal scrap originating as residues fromproduction processes, but it may also be metal collected from anothersource. The chemical composition of the metal is generally only knownapproximately. For the purpose of processing the metal removed from themelting apparatus further, its chemical composition should in general bebetween given tolerance limits. Corrections to the chemical composition,obtained after melting, of the molten metal are possible as a result ofdiluting the metal which forms the main constituent in the case ofunduly high concentrations of alloy elements or impurities, or by addingan alloy element if its concentration in the molten metal is unduly low.

The method described above can be performed as long as molten metal of aparticular composition or family of compositions has to be made andmetal scrap of a particular composition or family of compositions istherefore used.

A problem with the known melting apparatus and the method of operatingit arises if the chemical composition of the molten metal has to bealtered, for example in the event of an alloy change. From thedescription of the method, it follows that the bath of molten metal inthe melting apparatus functions as heat-transfer medium for transferringthe heat originating from the burners or another heat source in theburner chamber to the metal scrap to be melted. During the changeoverfrom a first chemical composition to a second chemical composition ofthe molten metal, it is therefore customary to empty the meltingapparatus until a bath of a certain size, also referred to as residualbath, of the first composition remains. Then metal of a flushingcomposition or of the second composition is added to the residual bath.In this operation, it is not always possible to obtain, with the metaladded, a bath whose chemical composition is within given limits. As aresult of emptying the melting apparatus again and filling it again withmetal of a flushing composition or of the second composition, theinfluence of the first composition on the composition of the bath can beconsiderably reduced. As a consequence of the undesired or incorrectcomposition, the bath contents removed will have no direct application.After it has solidified, the metal of incorrect composition can bestored and remelted at a later time. In this operation, a certain amountof metal will be lost as a result of oxidation.

The extent of dilution necessary to arrive at the desired composition ofthe bath plays a part in the determination of the size of the residualbath. In this process, metal of an undesired, incorrect composition maybe produced. A chosen residual bath having a volume of 20% of thenominal volume of the molten bath is conventional as a compromise.

The object of the invention is to provide a melting apparatus formelting metal with which it is possible to change the chemicalcomposition of the molten metal with a smaller residual bath thanhitherto customary and possible for production engineering reasons andwith which other advantages are also achievable.

These objects are achieved with the melting apparatus which, apart fromhaving circulation means which are suitable for transferring moltenmetal to a second or pressure connection of the melting chamber from afirst or suction connection of the burner chamber, according to theinvention is characterised in that the base of the melting chamber isinclined towards the inlet opening of the passage by a melting chambergradient, in that the base of the burner chamber is inclined with aburner-chamber gradient towards the suction connection and in that it isprovided with distribution means in order to spread the liquid metalemerging from the outflow opening over the base of the burner chamberfor the purpose of increasing the surface area of said base covered byliquid metal in a situation in which the level of the liquid level inthe melting apparatus is lower than the outflow opening.

It can be advantageous if the second or pressure connection is situatedhigher than the first suction connection in view of the mutual positionof the bases of the burner chamber and the melting chamber, that is tosay also if the base of the melting chamber is higher than that of theburner chamber or vice versa.

With the circulation means, molten metal can be transferred from theburner chamber to the melting chamber, where it comes into contact withmetal scrap to be melted and will cause the latter to melt, at leastpartly. The molten metal then flows towards the passage and via thepassage back to the burner chamber, where it is reheated and is taken upagain by the circulation means for renewed circulation. In the meltingchamber, a certain amount of metal can be melted for each circulation ofthe molten metal as just described and/or therefore per unit time. Thetime used for a circulation of the molten metal from melting chamber viaburner chamber back to melting chamber is appreciably shortened as aresult of the forced circulation. As a result, more heat can be fed tothe molten metal circulating between the chambers per unit time, andconsequently more metal can be melted per unit time than in the knownmelting apparatus.

It is possible with the invention to reduce the residual bathappreciably, with the result that a greater changeover in the chemicalcomposition of the bath is possible without a metal of incorrectcomposition being produced. Given a potential, large changeover in thechemical composition of the bath, the smaller residual bath results inan appreciably lower risk of metal of an incorrect composition beingproduced, as a result of which the risk in casting metal in solid formdecreases proportionately.

A preferred embodiment of the melting apparatus according to theinvention is characterised in that the circulation means comprise anelectromagnetic pump. Such a pump provides the advantage of a largeworking head, as a result of which a great degree of freedom is achievedin the construction of the melting apparatus. Another advantage is thatthe electromagnetic pump has few or no movable parts and is consequentlylow in maintenance and not susceptible to malfunction.

Particular advantages are achieved because the base of the meltingchamber is inclined with a melting-chamber gradient towards the inletopening of the passage, the melting-chamber gradient preferably beinginclined from the pressure connection towards the inlet opening of thepassage. Molten metal which is introduced into the melting chamber bythe circulation means via the pressure connection is able to leave themelting chamber through the passage to the burner chamber together withmetal additionally melted from the solid state in the melting chamber.This embodiment consequently contributes to the possibility of keepingthe residual bath in the melting apparatus low.

Also particular advantages are achieved because the base of the burnerchamber is inclined with a burner-chamber gradient towards the suctionconnection, the burner-chamber gradient preferably being inclinedtowards the suction connection from the outlet opening of the passage.It is possible with this embodiment to empty the burner chambersubstantially and therefore retain a smaller residual bath. In addition,this embodiment achieves the result that, as a result of theintervention of the circulation means, molten metal continues tocirculate even with a small residual bath, as a result of which heat canbe absorbed per unit time in the burner chamber and transferred to solidmetal to be melted in the melting chamber.

The inclined base of the burner chamber contributes, just as is the casefor the inclined base of the melting chamber, to a rapid flow of moltenmetal through the burner chamber and therefore to a large capacity forabsorbing heat per unit time and consequently to the melting capacity,even if the residual bath is chosen as small or in the case of a smallbath volume.

A particularly compact construction of the melting apparatus accordingto the invention is possible in the case of an embodiment which ischaracterised in that the direction in which the melting-chambergradient is inclined differs essentially from the direction in which theburner-chamber gradient is inclined and, more particularly, in that thedirection in which the melting-chamber gradient is inclined isessentially opposite to the direction in which the burner-chambergradient is inclined. The circulation means permit a greater freedom inthe construction of the furnace apparatus because the operation is nolonger dependent on just convection within the bath of molten metal.Within the possibilities of the chosen circulation means, there isfreedom of choice in the mutual positioning of the suction connectionand the pressure connection and, given an inclined base of the meltingchamber and/or burner chamber, also in the direction in which the baseof the one chamber is inclined with respect to the direction in whichthe base of the other chamber is inclined. In this connection, aparticularly compact construction can be achieved if both directionsextend essentially in an intersecting and opposite manner. Pipes andcomponents between suction connection and pressure connection, includingalso the circulation means, can then be positioned in the immediatevicinity of one another. Pipes which connect the suction connection andthe pressure connection to the circulation means can be short, as aresult of which little heat loss occurs and the flow resistance can beminimised. As a result of the choice of opposite directions ofinclination, the burner chamber and the melting chamber can beconstructed next to one another, resulting in low energy losses due tothe partition. Preferably, the passage extends in this case from aposition near the lowest region of the base of the melting chamber to aposition near the highest region of the base of the melting chamber.Preferably, the passage extends only over a limited part of thepartition near said regions. If circulation means are used, there islittle or no need for a large passage because there is no longerdependence on free convection.

During operation, liquid metal in the melting chamber will collect at ornear the lowest point as a consequence of the angle of inclination ofits base. If the average bath level in the burner chamber is lower underthese circumstances (allowing for the amount of metal in circulation)than the level of the base of the melting chamber near the passage, allthe liquid metal will flow back out of the melting chamber via thepassage into the burner chamber.

If the bath level in the burner chamber is higher than the level of thebase of the melting chamber (at the position of the inlet of thepassage), the liquid metal still flows towards the lowest point in themelting chamber. As a consequence of the circulation means used, all theliquid metal will be absorbed in the circuit.

Yet another advantage of this embodiment of the melting chamber is that,in a situation without forced metal circulation, a contribution istherefore effectively made to the attempt to minimise the residual bathunder all circumstances, that is to say regardless of the height of thebath in the burner chamber and possibly even in the melting chamber.

Another advantage of this embodiment of the melting chamber is that, ina situation with forced metal circulation, the flow of metal into themelting chamber from the pressure connection to the level of theresidual bath is accelerated. As a result, a contribution is made to theattempt to minimise the residual bath even in this situation.

Another embodiment of the melting apparatus which, according to theinvention, contributes to a large melting capacity with a small residualbath is characterised in that the melting apparatus is provided with atransport channel which is suitable for conveying molten metal betweenthe pressure connection and the inlet opening of the passage at least ina situation in which the base of the melting chamber is not completelycovered with liquid metal. Molten metal which enters the melting chamberthrough the pressure connection can be conveyed through the transportchannel, it being ensured that solid metal to be melted is also conveyedin the transport channel, for example by means of a suitable hopperchute.

In the situation of a low level of the bath, the solid metal in thetransport channel is in intimate contact with all, or with a large part,of the molten metal fed via the pressure connection, as a result ofwhich the chance of solidification of the solid metal, as in thesituation involving a small residual bath, is reduced and the meltingcapacity is increased in said situation. Preferably, the transportchannel is an open channel. A simple and expedient embodiment ischaracterised in that the transport channel is bounded by the base ofthe melting chamber and a wall of the melting chamber in which the inletopening is situated, which base and wall enclose an acute angle. Such atransport channel can easily be made by giving the base of the burnerchamber a gradient, as a result of which said base is inclined in thedirection of the wall, preferably the partition between the twochambers, the transport channel therefore being hounded by a part of thebase of the melting chamber and a part, adjacent thereto, of thepartition.

A further increase in the melting capacity is achieved because of thepresence of distribution means in order to spread the liquid metalemerging from the outflow opening over the base of the burner chamberfor the purpose of increasing the surface area of said base covered bythe liquid metal in a situation in which the level of liquid metal inthe melting apparatus is lower than the outflow opening.

Generally, the melting capacity is proportional to the bath surface areairradiated by the heat sources, such as burners. As has already beenstated above, as a result of the discharge gradient in the meltingchamber and the slope in the burner chamber, the bath surface areadecreases with decreasing bath content. As a result of spreading themolten metal introduced into the burner chamber or present therein, suchas the residual bath, over as large a part as possible of the base ofthe burner chamber, a large irradiated surface area is obtained even inthe case of a small residual bath.

According to the invention it is now also possible to more effectivelyretain the dross in the melting chamber which gives the additionaladvantage that the heat transfer to the molten metal in the burnerchamber is maximised.

The invention is also embodied in a method for melting a metal such asaluminium, in which molten metal is removed from a burner chamber andtransported by means situated outside the burner chamber and the meltingchamber to a melting chamber, the melting chamber and the burner chamberbeing hydraulically coupled to one another and, in which an apparatusaccording to the invention is used.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained below by reference to the drawing of anon-restrictive embodiment of a melting apparatus according to theinvention. In the drawing:

FIG. 1 shows a diagrammatic plan view of a cross section of a meltingapparatus according to the invention,

FIG. 2 shows a diagrammatic front view of a section along the line AA inFIG. 1,

FIG. 3 shows a diagrammatic side view of a section along the line BB inFIG. 1.

In the figures, corresponding elements or elements having identicalfunctions have corresponding reference numerals.

In FIG. 1, 1 is a melting apparatus in which the invention is embodied.The melting apparatus comprises a melting chamber 2 and a burner chamber3, which are separated from one another by a partition 4. The meltingapparatus comprises on its outside a heat-insulating and heat-resistantoutside wall 5. Partition 4 is also heat-resistant, but, for a betterheat transfer between melting chamber and burner chamber, can have ahigh thermal conductivity. The partition 4 extends from the ceiling 6(see FIG. 2) to both the base 7 of the melting chamber and the base 8 ofthe burner chamber and is provided with a localised passage 9.Preferably, means are fitted in or near the passage for retaining orremoving slag produced in the melting chamber. Passage 9 has an inletopening 10 on the melting-chamber side and an outlet opening 11 on theburner-chamber side. The base 7 of the melting chamber is inclined inthe direction of arrow 12 from the second or pressure connection 13 tothe inlet opening 10. Base 7 is also inclined from side wall 14, whichforms part of the wall 5, towards the partition 4 in the direction ofarrow 15. Partition 4 and base 7 enclose an acute angle a (see FIG. 2).Side wall 14 is provided with a charging opening 16 behind which adischarge chute 17 is positioned for the introduction via the latter ofmetal to be melted. Burner chamber 3 has a base 8 which is inclined inthe direction indicated by the arrow 18 from the inlet opening 11 in thedirection of the first suction connection 19.

In the rear wall 25, which forms part of the outside wall 5, a burner 26is positioned which is provided with connecting pipes 27 and 28 forconnection to an oxygen source and fuel source, which is not shown. Fluegases which are produced in the burner by combustion of the fuel withoxygen, can be removed via flue-gas outlet 29 (see FIG. 2). In side wall30, which is part of outside wall 5, a closable tapping opening 31 isfitted via which molten metal can be removed from the melting apparatus.

Near the outflow opening 11, base 8 is provided with distribution meansin the form of a number of distribution channels 20, 21, 22, 23, 24 inorder to spread liquid metal, which flows into the burner chamberthrough the passage, over as large a part as possible of base 8.

Connected to suction connection 19 by means of a suction pipe 32 is apump 33, preferably an electromagnetic pump. The outlet of the pump 33is connected by means of a coupling pipe 34 to a so-called loadingcistern 35, which is connected by means of pipe 36 to the pressureconnection 13. The loading cistern can be included in order to meltfinely divided solid particles rapidly. If desired, a slag-removalvessel 40, which is not shown in greater detail, can also be included inpipe 36 to remove slag floating on the liquid metal. Liquid metal canalso be removed from the loading cistern or from the slag-removalvessel. With the circulation means, a greater freedom is also obtainedin the positioning of the loading cistern and the slag-removal vessel,in particular, as regards the level of the bases thereof with regard toliquid metal remaining behind.

FIG. 2 diagrammatically shows a front view of a section along the lineAA in FIG. 1. Arrow 15 indicates that base 7 is inclined in thedirection of the arrow from side wall 14 towards partition 4.

FIG. 3 shows a diagrammatic side view of a section along the line BB inFIG. 1. The figure reveals the opposite and intersecting course of thetwo bases 7 and 8, a passage 9 being fitted between a low region, andpreferably the lowest region, of base 7 and a high region, andpreferably the highest region, of base 8.

The working and the operation of the melting apparatus proceed asfollows:

During normal use, the melting apparatus is charged with liquid metal,such as liquid aluminium, to the level shown by the indication line P.

In changing over from the one, first alloy or composition of the metalto be melted to another, second alloy or composition to be melted,molten first alloy is removed via tapping opening 31 until a residualbath of desired size is left. This size can be chosen to be very small,in principle it is sufficient that the suction opening 19 remainsadequately covered and that sufficient molten material is present in thecirculation part, comprising the elements 32, 33, 34, 35, 36 andslag-removal vessel 40, which is not shown, for a good operationthereof. It is pointed out in this connection that the loading cistern35 and the slag-removal vessel 40 are optional. The melting apparatusitself can be virtually completely free of molten metal of the firstalloy. The liquid metal which forms the residual bath is passed throughsuction opening 19 via pipe 32 to pump 33 and is after passing through aslag-removal vessel 40, to pressure connection 13. Via pressureconnection 13, the liquid metal finishes up on base 7 and, on the onehand, flows down as a consequence of the gradient indicated by arrow 12and, on the other hand, as a consequence of the gradient indicated byarrow 15 in the direction of the partition 4. As a consequence of thetwo gradients mentioned, the molten metal therefore flows initiallyessentially through a transport channel 50 which is bounded by parts,adjoining at the angle a, of the partition 4 and the base 7.

Solid metal is introduced into the liquid metal flowing through thetransport channel 50 through charging opening 16 via hopper chute 17, asa result of which at least part of the solid metal melts, which partflows along with the liquid metal introduced through the pressureconnection 13 to and through passage 9. The molten metal, now cooled, isspread over the base 8 of the burner chamber by the distribution meansformed by the distribution channels 20-24. In the burner chamber, fuel,supplied via pipe 28, is burnt with oxygen, supplied via pipe 27, byburner 26. A relatively small amount of molten metal has a largeirradiatable surface area as a result of having been spread over a largepart of the base of the burner chamber and can consequently absorb muchof the heat generated by the burner on its downward path over the base8. The molten metal heated in this way ends up at suction opening 19 andis circulated in the melting apparatus in the manner described. Thevolume of molten metal increases continuously as a result of addingsolid metal which is melted in the melting chamber. The molten metal isa mixture of the first alloy and the second alloy. If desired, toaccelerate the dilution of the first alloy with the second alloy, themelting apparatus can be emptied again in the meantime down to a desiredresidual bath, after which solid metal of the second alloy can beintroduced again into the melting chamber. The metal removed has anincorrect composition and is stored in order to be melted again orprocessed at a suitable point later in time. As a result of melting moremetal than is introduced, the level of the molten metal in the bathrises, as a result of which base 8 is completely covered, passage 9 hasa full flow and, finally, base 7 is covered. The level can be increasedfurther to a desired height, such as the nominal height indicated by P.

The two bases 7 and 8 each have a drop between pressure connection andpassage or passage and suction connection, respectively, ofapproximately 10 to 15 cm over a distance of approximately 6 m.

Where a passage has been mentioned above, it will be clear to the personskilled in the art that this is also to be understood as meaning anopening in a wall, such as a partition. In the above, reference is madeto a chamber as burner chamber. It is clear that forms of heatgeneration other than by means of a burner are also possible. Wheremention has been made of a suction connection, that term includes anyconnection for removing molten metal for transportation to thecirculation means, just as the term pressure connection includes anyconnection which is suitable for conveying molten metal originating fromthe circulation means into the melting apparatus.

It will be obvious to the person skilled in the art that the inventionand its embodiment can also be applied to a melting apparatus in whichmelting chamber and burner chamber are combined to form a single chamberprovided with a sloping base and in which the circulation means aresuitable or used for transporting molten metal from the one region ofthe melting apparatus to another region, preferably situated higher, ofthe melting apparatus. As a result of feeding to a more highly situatedregion, advantages are achieved, such as described above for a meltingapparatus having two chambers.

What is claimed is:
 1. Melting apparatus for melting a metal,comprising:a melting chamber (2) which comprises a base, a burnerchamber (3), a passage (9) which extends between the melting chamber (2)and the burner chamber (3) and which has an inlet opening (10) on themelting-chamber side and an outlet opening (11) on the burner-chamberside for allowing molten metal to pass from the melting chamber (2) tothe burner chamber (3), circulation means (33) suitable for transferringthe molten metal to a second or pressure connection (36) of the meltingchamber (2) from a first or suction connection (32) of the burnerchamber (3), wherein the base (7) of the melting chamber is inclinedtowards the inlet opening (10) of the passage (9) by a melting-chambergradient, the base (8) of the burner chamber (3) is inclined with aburner-chamber gradient towards the suction connection, and the base (8)of the burner chamber (3) comprises distribution means to spread theliquid metal, emerging from the outlet opening, over the base (8) of theburner chamber for the purpose of increasing the surface area of saidbase (8) of the burner chamber (3) covered by liquid metal in asituation in which the level of the liquid level in the meltingapparatus is lower than the outflow opening.
 2. Melting apparatusaccording to claim 1, wherein the circulation means (33) comprise anelectromagnetic pump.
 3. Melting apparatus according to claim 1, whereinthe direction in which the melting-chamber gradient is inclined differsessentially from the direction in which the burner-chamber gradient isinclined.
 4. Melting apparatus according to claim 3, wherein thedirection in which the melting-chamber gradient is inclined isessentially opposite to the direction in which the burner-chambergradient is inclined.
 5. Melting apparatus according to claim 1 whereincharacterised in that the melting apparatus is provided with a transportchannel which is suitable for conveying molten metal between thepressure connection and the inlet opening of the passage at least in asituation in which the base of the melting chamber is not completelycovered with liquid metal.
 6. Melting apparatus according to claim 5,wherein the transport channel is bounded by the base of the meltingchamber and a wall of the melting chamber in which the inlet opening issituated, which base and wall enclose an acute angle.
 7. Method formelting a metal, comprising: melting the metal in an apparatuscomprising:a melting chamber (2) which comprises a base, a burnerchamber (3), a passage (9) which extends between the melting chamber (2)and the burner chamber (3) and which has an inlet opening (10) on themelting-chamber side and an outlet opening (11) on the burner-chamberside for allowing molten metal to pass from the melting chamber (2) tothe burner chamber (3), circulation means (33) suitable for transferringmolten metal to a second or pressure connection (36) of the meltingchamber (2) from a first or suction connection (32) of the burnerchamber (3), wherein the base (7) of the melting chamber is inclinedtowards the inlet opening (10) of the passage (9) by a melting-chambergradient, the base (8) of the burner chamber (3) is inclined with aburner-chamber gradient towards the suction connection, and the base (8)of the burner chamber (3) comprises distribution means to spread theliquid metal, emerging, from the outlet opening, over the base (8) ofthe burner chamber for the purpose of increasing the surface area ofsaid base covered by liquid metal in a situation in which the level ofthe liquid level in the melting apparatus is lower than the outflowopening; passing the molten metal from the melting chamber (2) to theburner chamber (3) through the passage (9); and removing the moltenmetal from the burner chamber and transporting the molten metal by thecirculation means, situated outside the burner chamber and the meltingchamber, to the melting chamber, the melting chamber and the burnerchamber being hydraulically coupled to one another.
 8. Melting apparatusaccording to claim 2, wherein the direction in which the melting-chambergradient is inclined differs essentially from the direction in which theburner-chamber gradient is inclined.
 9. Melting apparatus according toclaim 8, wherein the direction in which the melting-chamber gradient isinclined is essentially opposite to the direction in which theburner-chamber gradient is inclined.
 10. Melting apparatus according toclaim 2, wherein the melting apparatus is provided with a transportchannel which is suitable for conveying molten metal between thepressure connection and the inlet opening of the passage at least in asituation in which the base of the melting chamber is not completelycovered with liquid metal.
 11. Melting apparatus according to claim 10,wherein the transport channel is bounded by the base of the meltingchamber and a wall of the melting chamber in which the inlet opening issituated, which base and wall enclose an acute angle.
 12. Methodaccording to claim 7, wherein the circulation means (33) comprise anelectromagnetic pump and the molten metal being transferred from thefirst or suction connection (32) of the burner chamber (3) to the secondor pressure connection (36) of the melting chamber (2) passes throughthe electromagnetic pump.
 13. Method according to claim 7, wherein themolten metal travels along the melting chamber base at themelting-chamber gradient which is inclined in a direction which differsessentially from the direction in which the burner-chamber gradient isinclined.
 14. Method according to claim 13, wherein the molten metaltravels along the melting chamber base at the melting-chamber gradientwhich is inclined in a direction which is essentially opposite to thedirection in which the burner-chamber gradient is inclined.
 15. Methodaccording to claim 7, wherein the molten metal is conveyed between thepressure connection and the inlet opening of the passage through atransport channel when the base of the melting chamber is not completelycovered with liquid metal.
 16. Method according to claim 15, wherein themolten metal is conveyed between the pressure connection and the inletopening through the transport channel which is bounded by the base ofthe melting chamber and a wall of the melting chamber in which the inletopening is situated, which base and wall enclose an acute angle. 17.Method according to claim 12, wherein the molten metal travels along themelting-chamber gradient is inclined differs essentially from thedirection in which the burner-chamber gradient is inclined.
 18. Methodaccording to claim 17, wherein the molten metal travels along themelting chamber base at the melting-chamber gradient which is inclinedin a direction which is essentially opposite to the direction in whichthe burner-chamber gradient is inclined.
 19. Method according to claim12, wherein the molten metal is conveyed between the pressure connectionand the inlet opening of the passage through a transport channel whenthe base of the melting chamber is not completely covered with liquidmetal.
 20. Method according to claim 19, wherein the molten metal isconveyed between the pressure connection and the inlet opening throughthe transport channel which is bounded by the base of the meltingchamber and a wall of the melting chamber in which the inlet opening issituated which base and wall enclose an acute angle.
 21. Methodaccording to claim 7, wherein the molten metal comprises aluminum and ismelted.
 22. Method according to claim 12, wherein the molten metalcomprises aluminum, and is melted.